Camshaft phasers for varying the timing of valves in internal combustion engines are well known. A typical phaser comprises a rotor, attached to a camshaft, and a stator surrounding the rotor and driven in time with an engine crankshaft. The phaser is able to vary the angular position of the rotor with respect to the stator and thus to vary the valve timing imposed on the camshaft with respect to the crankshaft and pistons.
A phaser may include an external timing wheel, having notches or other indicia, fixedly attached to the rotor such that the angular position of the rotor within the stator may be determined at any time by interrogating the target wheel. A prior art target wheel preferably is formed by stamping from sheet metal to minimize the mass and inertia of the wheel. In the prior art, the target wheel is indexed to the rotor during assembly of the phaser. However, it has been found that the tolerance stackup of the components is such that indexing by this method is insufficiently precise for maximizing engine control. What is need in the art is an improved method for indexing a timing wheel to a camshaft phaser rotor.
It is a principal object of the present invention to provide retention and to improve the indexing precision of a camshaft phaser timing wheel to a phaser rotor in order to improve performance of an engine to which the phaser is eventually mounted.